Pollen morphology of Taiwanese Asparagaceae species: insights from scanning electron microscopy

Abstract

This study employed scanning electron microscopy to investigate the pollen morphology of Taiwanese Asparagaceae species, revealing that their pollen morphology closely aligns with that of other monocotyledonous plant taxa such as Asparagales, Commelinales, and Bromeliales. Despite the overall similarity, variations in pollen morphology across different genera were noted, highlighting its potential utility in classification. Unlike the wide diversity observed in flower morphology, Asparagaceae pollen morphology appears conservative, rendering it less effective as a taxonomic marker at the species level. The study also delved into the effects of pollenkitt and harmomegathy on pollen morphology, discovering that pollenkitt partially or completely coats the pollen surface, potentially complicating the identification of exine sculpture. Furthermore, the harmomegathic effect was observed to influence aperture dynamics. Consequently, observing both hydrated and dried pollen is advisable, as it can more accurately depict the pollen’s aperture morphology and offer additional insights for pollen grain analysis.

Keywords:

• pollen morphology
• Asparagaceae
• scanning electron microscopy
• pollenkitt
• harmomegathy

Acknowledgements

We thank Ms. Yuan-Chien Lin and Ms. Tai-Chen Ho for field assistance.

Disclosure statement

The authors declare no conflict of interest.

Plate 7. Pollen morphology of Peliosanthes. 1–5: P. arisanensis; 6–10: P. kaoi. 1, 6: distal polar view; 2, 7: proximal polar view; 3, 8: equatorial view; 4, 9: sculpture of distal polar view; 5, 10: sculpture of proximal polar view. Scale bar: 1, 2, 3, 6, 7, 8 = 10 μm, others = 1 μm.

Plate 8. Pollen morphology of Disporopsis and Heteropolygonatum. 1–5: D. pernyi; 6–10: H. altelobatum. 1, 6: distal polar view; 2, 7: proximal polar view; 3, 8: equatorial view; 4, 9: sculpture of distal polar view; 5, 10: sculpture of proximal polar view. Scale bar: 1, 2, 3, 6, 7, 8 = 10 μm, others = 1 μm.

Plate 9. Pollen morphology of Maianthemum. 1–5: M. formosana; 6–10: M. harae. 1, 6: distal polar view; 2, 7: proximal polar view; 3, 8: equatorial view; 4, 9: sculpture of distal polar view; 5, 10: sculpture of proximal polar view. Scale bar: 1, 2, 3, 6, 7, 8 = 10 μm, others = 1 μm.

Plate 10. Pollen morphology of Polygonatum. 1–5: P. arisanensis var. arisanensis; 6–9: P. arisanensis var. chingshuishanianum; 10–14: P. arisanensis var. formosanum. 1, 6, 10: distal polar view; 2, 7, 11: proximal polar view; 3, 12: equatorial view; 4, 8, 13: sculpture of distal polar view; 5, 9, 14: sculpture of proximal polar view. Scale bar: 1, 2, 3, 6, 7, 10, 11, 12 = 10 μm, others = 1 μm.

Plate 11. Pollen morphology of Thysanotus chinensis. 1: pollen grain; 2: sculpture of shield-like structure; 3: sculpture of grooves. Scale bar: 1 = 10 μm, 2, 3 = 1 μm.

Plate 12. Pollen morphology of Barnardia japonica. 1: distal polar view; 2: proximal polar view; 3: equatorial view; 4: sculpture of distal polar view; 5: sculpture of proximal polar view. Scale bar: 1, 2, 3 = 10 μm, 4, 5 = 1 μm.

Plate 13. Morphology of dry pollen grain with different aperture types. 1: monosulcate (Liriope spicata); 2: ulcus (Dracaena angustifolia); 3: omniaperture (Aspidistra attenuata); 4: clypeate (Thysanotus chinensis). Scale bar = 10 μm.

Figure 1. Hierarchical clustering dendrogram of Asparagaceae species from Taiwan. The analysis was based on Gower's distance and employed Ward's linkage method. The red dashed line at 0.6 represents a suggested threshold for three clusters' division.

Additional information

Funding

This study was supported by the National Science and Technology Council under Grant no. MOST 103-2313-B-005-009-MY3 to Yen-Hsueh Tseng and NSTC 112-2621-B-003-001-MY3 to Chien-Ti Chao.